The National Cancer Institute funded a proposal in 1977 to plan a multiinstitutional study of childhood brain tumors. As a result, a Childhood Brain Tumor Consortium (CBTC) of multiple institutions located in North America has been planned, which will combine the efforts of neuropathologists, pediatric pathologists, a neuroepidemiologist, neurosurgeons, and biostatisticians. Our principal goal is to obtain accurate prognostic information for childhood brain tumors at each specific site within the brain, as a baseline for the design of therapy for individual children, and for the design of studies of competing therapies. We have assembled the resources of eleven institutions with active pediatric neurosurgical services into a consortium. The estimated large data base from these institutions is between 3,000 and 3,400 children. We plan to use the first biopsy sample for the estimate of the prognostic significance of individual histologic features and clinical features. We plan to use two classifications, that of the World Health Organization, and another one which uses the biologic characteristics of clustering of histologic features and life tables. We will choose which of these classifications provides the most accurate prognostic information for tumors at each specific site within the brain. This information will be entered into an interactive computer program which will provide: (1) Specific prognostic information for tumors at each of several sites within the brain for individual patient care decisions for any pathologist or neurosurgeon, and 2) Prognostic information for the design of studies of competing therapies. Auxiliary studies are planned. These include standardization of histologic criteria, methods of decreasing observational variation, other tissue markers of malignancy, homogeneity of tumor, multivariate analyses applied to pathology, and others.